static unsigned burst_modulate(unsigned burst, uint64_t available) {
unsigned k;
/* Modulates the burst rate a bit with the amount of available
* disk space */
k = u64log2(available);
/* 1MB */
if (k <= 20)
return burst;
burst = (burst * (k-16)) / 4;
/*
* Example:
*
* <= 1MB = rate * 1
* 16MB = rate * 2
* 256MB = rate * 3
* 4GB = rate * 4
* 64GB = rate * 5
* 1TB = rate * 6
*/
return burst;
}
static void test_u64log2(void) {
assert_se(u64log2(0) == 0);
assert_se(u64log2(8) == 3);
assert_se(u64log2(9) == 3);
assert_se(u64log2(15) == 3);
assert_se(u64log2(16) == 4);
assert_se(u64log2(1024*1024) == 20);
assert_se(u64log2(1024*1024+5) == 20);
}
static void test_u64log2(void) {
log_info("/* %s */", __func__);
assert_se(u64log2(0) == 0);
assert_se(u64log2(8) == 3);
assert_se(u64log2(9) == 3);
assert_se(u64log2(15) == 3);
assert_se(u64log2(16) == 4);
assert_se(u64log2(1024*1024) == 20);
assert_se(u64log2(1024*1024+5) == 20);
}
/*
* initialize the computed parameters for an index
*/
static ISect*
initisect1(ISect *is)
{
u64int v;
is->buckmax = (is->blocksize - IBucketSize) / IEntrySize;
is->blocklog = u64log2(is->blocksize);
if(is->blocksize != (1 << is->blocklog)){
seterr(ECorrupt, "illegal non-power-of-2 bucket size %d\n", is->blocksize);
freeisect(is);
return nil;
}
partblocksize(is->part, is->blocksize);
is->tabbase = (PartBlank + HeadSize + is->blocksize - 1) & ~(is->blocksize - 1);
if(is->tabbase >= is->blockbase){
seterr(ECorrupt, "index section config table overlaps bucket storage");
freeisect(is);
return nil;
}
is->tabsize = is->blockbase - is->tabbase;
v = is->part->size & ~(u64int)(is->blocksize - 1);
if(is->blockbase + (u64int)is->blocks * is->blocksize != v){
seterr(ECorrupt, "invalid blocks in index section %s", is->name);
/* ZZZ what to do?
freeisect(is);
return nil;
*/
}
if(is->stop - is->start > is->blocks){
seterr(ECorrupt, "index section overflows available space");
freeisect(is);
return nil;
}
if(is->start > is->stop){
seterr(ECorrupt, "invalid index section range");
freeisect(is);
return nil;
}
return is;
}